The Graph is a decentralized protocol for indexing and querying data from blockchains. Anyone can build and publish open APIs, called subgraphs, making data easily accessible in a decentralized and reliable way. Subgraphs make it possible for anyone to query data that would otherwise be difficult to query on-chain directly. Each subgraph pays attention to events of a project’s contracts and maps that event data to data that The Graph stores in its database. Learn more about The Graph here.
GraphQL is the underlying query language utilized in The Graph. GraphQL is especially useful for calls requiring lots of information where instead of making multiple API calls one only needs to do one subgraph call to get all of the information needed. Learn more about GraphQL here.